Field
Aspects of the present invention generally relate to a power receiving apparatus for wirelessly receiving power from an external apparatus.
Description of the Related Art
In wireless power transmission, electromagnetic waves radiated from an antenna of a power transmission apparatus (power transmission antenna) are received by an antenna of a power receiving apparatus (power receiving antenna) to drive the power receiving apparatus or charge a rechargeable battery of the power receiving apparatus. To prevent radiation of electromagnetic waves in an uncontrolled state, it is common practice that control information including wireless power transmission parameters is exchanged between the power transmission apparatus and the power receiving apparatus in advance, and the power transmission apparatus has power transmission/reception control incorporated therein for supplying power determined by the control information to the power receiving apparatus.
Among various frequencies for wireless power transmission, there is proposed a wireless power transmission method in which 6.78 MHz or 13.56 MHz of a HF (high frequency) band is used as a wireless power carrier frequency.
A contactless IC card uses 13.56 MHz of a HF band as a carrier frequency for wireless communication with a contactless IC card reader/writer. A power receiving apparatus can be mounted with a contactless IC function or a contactless IC reader/writer function.
A secondary harmonic 13.56 MHz of a wireless power transmission carrier frequency 6.78 MHz overlaps 13.56 MHz as a carrier frequency of a contactless IC function. Therefore, electromagnetic waves carrying power radiated from a power transmission apparatus might cause such an effect as overloading or heat generation to a contactless IC and a contactless IC reader/writer. Even when not mounted on a power receiving apparatus, a contactless IC card unintentionally located nearby might be given such an effect of heat generation by a wireless power transmission carrier or the like as well.
Japanese Patent Laid-Open No. 2012-65455 recites that while receiving strong electromagnetic waves exceeding a predetermined value by a power receiving coil, a resonance frequency of a communication antenna used in close proximity contactless communication is shifted to reduce a voltage applied to an IC chip connected to the communication antenna.
Japanese Patent Laid-Open No. 2014-33504 recites protecting a communication circuit by cutting off a switch between a communication antenna and the communication circuit while a rechargeable battery of a power receiving apparatus is charged by wireless power transmission.
In the technique recited in Japanese Patent Laid-Open No. 2012-65455, an electromagnetic wave (communication signal) in close proximity contactless communication causes both a communicating coil and a power receiving coil to generate an induced current, so that the induced current generated on the power receiving coil side will be lost. This contributes to a reduction of a communication distance in close proximity contactless communication.
In the technique recited in Japanese Patent Laid-Open No. 2014-33504, the switch located between the communication antenna and the communication circuit serves as a loss of an induced current generated at the communication antenna during communication, which also contributes to a reduction of a communication distance.
In both the techniques recited in Japanese Patent Laid-Open No. 2012-65455 and Japanese Patent Laid-Open No. 2014-33504, at least one coil or antenna is in a state of resonance with a frequency of an electromagnetic wave from a power transmission apparatus during close proximity contactless communication and during a charging period. This makes it difficult to detect an unintentional location of a contactless IC card equipped with an antenna resonating with this frequency.